It is known that the takeoff of aircrafts should meet safety requirements being defined by the air regulation. In particular, when an engine breakdown occurs upon the takeoff of an aircraft, it is necessary to make sure that flying over obstacles such as mountains, antennas, trees or buildings, being located in the vicinity of the takeoff runway along the trajectory followed by the aircraft, remains possible, and this, with a sufficient safety margin.
Such a constraint could require the crew to limit the maximum takeoff weight of the aircraft, so as to allow the latter to generate a climbing slope sufficient for avoiding the obstacles.
In order to reduce the extent of such a constraint on the value of the maximum weight, an auxiliary takeoff trajectory (commonly referred to using the English acronym EOSID, for <<Engine Out Standard Instrument Departure>>) enabling a takeoff with a defective engine is determined in addition to a rectilinear standard takeoff trajectory (commonly referred to using the English acronym SID, for <<Standard Instrument Departure>>) being contemplated for a takeoff of the aircraft without any engine breakdown. Such an auxiliary takeoff trajectory diverges, at a divergence point, from the standard takeoff trajectory (being thus defined for an aircraft having all the engines thereof operating normally). Said takeoff (standard and auxiliary) trajectories allow to fly over obstacles located along their respective lateral profiles. The auxiliary takeoff trajectory that enables to by-pass high obstacles thus allows for a higher maximum takeoff weight than the standard takeoff trajectory.
Said divergence point is defined so that, if an engine breakdown occurs upstream (or at the level) of such a divergence point, the pilot turns off the aircraft to the auxiliary takeoff trajectory when the aircraft reaches said divergence point. On the other hand, if the engine breakdown occurs when the aircraft has exceeded the divergence point, the pilot continues the takeoff of the aircraft on the standard takeoff trajectory.
Furthermore, a decision speed is known, being defined so that, if an engine breakdown occurs while running on the runway for taking off while the aircraft has not reached such a decision speed yet, the remaining runway length is sufficient for allowing the aircraft to slow down and to stop within the boundaries of the runway. On the other hand, when an engine breakdown occurs while the speed of the aircraft is equal to or higher than such a decision speed, the aircraft is no longer able to stop on the remaining runway length and should therefore continue the takeoff.
A method for determining an EOSID auxiliary takeoff trajectory is known. Such a method is implemented either directly by airline companies when they have available a department able to perform such a task successfully, or by the aircraft manufacturer. This is a laborious task requiring the interactive use of several specific softwares and could take up to one week of work for a specialized team. Despite the use of softwares, such a usual method thus supposes a significant and expensive human involvement.
In addition, such a known method does not take into consideration, for determining the auxiliary takeoff trajectory, a possible engine breakdown occurring at a speed of the aircraft higher than the decision speed. Now, in such a situation, the effective speed of the aircraft on the auxiliary takeoff trajectory from the divergence point is higher than the speed of the aircraft contemplated for an engine breakdown occurring at the decision speed.
Since the turn radius is an increasing function of the aircraft speed and a decreasing function of the rolling angle of the aircraft, the follow-up of the piloting instructions for the nominal auxiliary takeoff (that is, established for an engine breakdown occurring at the decision speed), for which turns are taken at constant rolling, for example at 15 degrees, results in more significant turn radii than for a breakdown at the decision speed. Too late an engine breakdown could therefore result in an effective auxiliary takeoff trajectory, the ground track of which substantially differs from that of the nominal auxiliary takeoff trajectory, that could create collision risks with obstacles, more particular in a mountain area.
Furthermore, if an auxiliary takeoff trajectory has been found allowing for the takeoff of the aircraft at a high maximum weight, it is not ensured that the aircraft will be able to fly over, with such a high maximum weight, obstacles on the standard takeoff trajectory with all its engines in operation, and all the more with an engine breakdown occurring after the divergence point.
The present invention aims at remedying such drawbacks and determining an optimum auxiliary takeoff trajectory regarding the maximum takeoff weight, while meeting the regulation constraints (calculated for breakdown occurring at the decision speed) and ensuring flying over obstacles for an engine breakdown occurring at any subsequent time.